火场通风与火灾烟气痕迹的关联性研究

发布时间：2018-04-05 19:14

本文选题：火灾调查　切入点：烟熏痕迹　出处：《天津商业大学》2013年硕士论文

【摘要】：壁面烟熏痕迹是火灾调查工作中的重要研究内容，在某些火灾现场，由于地面痕迹和燃烧剩余产物在扑救的过程中被破坏，壁面烟熏痕迹的研究价值就变得尤为重要。火灾壁面烟熏痕迹形成的主要原因是火灾烟气中的游离碳等物质被吸附到壁面表面或缝隙中。所以，要研究壁面烟熏痕迹的形成规律，首先要研究火灾烟气的运动。影响火灾烟气运动的因素有很多，本文主要探究火场通风对火灾烟熏痕迹形成规律的影响，通过理论模型分析、实体模型实验和数值模拟来研究探讨相关规律。本文在分析前人研究成果的基础上，，首先利用点源模型理论，通过使用抛物线来表征壁面V型烟熏痕的迹轮廓曲线，确定了无风条件下火源烟气羽流与壁面位置关系对V型烟熏痕迹的影响，并依据实验测量结果拟合出了烟羽流的锥体母线。在此基础之上，在模型房间内设置了三种不同布局的火源，通过实验研究自然排烟和机械排烟条件下，室内火灾壁面烟熏痕迹的变化规律。室内火源布局为中心火时，自然排烟条件下壁面痕迹的最薄处应处于火源的正上方。通风使得壁面顶部烟熏痕迹的厚度降低，火源燃烧时间缩短，并导致烟熏痕迹最薄处向排烟口方向发生明显偏移，影响对起火点的准确判定。室内火源布局为壁面火时，通风使得壁面顶部烟熏痕迹的厚度显著降低，火源燃烧时间显著缩短，同时还强化了壁面V型痕迹的轮廓特征：即与自然排烟条件下的痕迹相比，机械通风条件下的壁面V型痕迹轮廓明显增大，整体微微向排烟口倾斜，辨识起火点更容易。室内火源布局为墙角火时，墙角处的壁面能形成清晰的V形痕迹，易于辨识起火点。由于火源位于模型房间门口的墙角，通风仅能使壁面顶部烟熏痕迹的厚度减小，对燃烧时间和烟气温度影响不大。可见，如果火源位置临近火场进气口或排烟口，机械排烟对壁面痕迹的影响并不大。计算机数值模拟实验通过计算烟气浓度来表征壁面痕迹的分布，实验精度较高。与实际照片中的烟熏痕迹实验比较下来，中心火和墙角火的模拟结果很接近，壁面火的V形痕迹无法准确的用浓度分布图来表征，故模拟精度较差。总体来讲，模拟实验的结果可靠。
[Abstract]:Smoke trace on wall is an important research content in fire investigation. In some fire sites, the research value of smoke trace on wall becomes particularly important because of the destruction of the surface trace and the residual product of burning in the process of extinguishing the fire.The main reason for the smoke marks of the fire wall is that the free carbon in the fire smoke is absorbed into the wall surface or gap.Therefore, in order to study the formation of smoke traces on the wall, the first step is to study the movement of fire smoke.There are many factors that affect the smoke movement in fire. This paper mainly explores the influence of fire ventilation on the formation law of smoke traces of fire, and through theoretical model analysis, solid model experiment and numerical simulation to study the relevant laws.In this paper, based on the analysis of previous research results, firstly, using point source model theory, parabola is used to characterize the contour curve of the V-shaped smoke mark on the wall.The influence of the relationship between the smoke plume and the wall position of the fire source on the smoke trace of V-type smoke was determined, and the pyramidal busbar of the plume was fitted according to the experimental results.On the basis of this, three kinds of fire sources with different layout were set up in the model room. The changes of smoke traces on the wall of indoor fire were studied by experiment under the condition of natural smoke exhaust and mechanical smoke exhaust.When the layout of indoor fire source is the central fire, the thinnest part of the wall trace should be located directly above the fire source under the condition of natural smoke exhaust.Ventilation reduces the thickness of smoke marks at the top of the wall, shortens the burning time of the fire source, and results in obvious deviation from the thinnest part of the smoke smoke trace to the outlet, which affects the accurate determination of the fire point.When the indoor fire source layout is wall fire, ventilation reduces the thickness of smoke trace at the top of the wall and shortens the burning time of the fire source. At the same time, it also strengthens the contour characteristics of the V-shaped trace on the wall: that is, compared with the trace under the condition of natural smoke exhaust,Under mechanical ventilation, the contour of V-shaped trace on the wall increases obviously, and the whole slightly inclines to the vent, so it is easier to identify the fire point.When the interior fire source layout is corner fire, the wall at the corner can form clear V-shaped trace, and it is easy to identify the fire point.Because the fire source is located in the corner of the door of the model room, ventilation can only reduce the thickness of smoke trace at the top of the wall, and has little effect on the burning time and flue gas temperature.It can be seen that if the source of fire is near the air inlet or exhaust port, the influence of mechanical smoke exhaust on the wall trace is not great.Computer numerical simulation experiments show that the distribution of wall traces is characterized by calculating the smoke concentration, and the experimental accuracy is high.Compared with the smoke trace experiments in the actual photographs, the simulation results of the central fire and the corner fire are very close. The V-shape trace of the wall fire can not be accurately characterized by the concentration distribution map, so the simulation accuracy is poor.In general, the simulation results are reliable.
【学位授予单位】：天津商业大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU998.12

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